The present invention is concerned with an apparatus for the separation of suspensions and solutions by means of electrophoresis. Various types of electrophoretic separations are known, including continuous free-boundary electrophoresis, exemplified by Bier, U.S. Pat. No. 2,878,178; electrodecantation, exemplified by Polson, U.S. Pat. No. 2,801,962; and forced flow electrophoresis, exemplified by Bier, U.S. Pat. No. 3,079,318.
Separations utilizing electrophoretic migration of an electrically charged colloidal component through a colloid permeable membrane are known and can be carried out on known apparatus after modification in accordance with the invention. Such apparatus typically comprises a compartment defined by a pair of semipermeable membranes which separate the compartment from a pair of electrodes, and at least one colloid permeable boundary membrane which divides the compartment into at least one pair of cells. Many apparatus will include a stack of cell pairs, each pair being separated by a semipermeable membrane. Appropriate fluid inlets and outlets, and appropriate electrical circuitry are provided to pass fluids through the cell pairs and to apply a direct current electric field across the permeable membrane. Apparatus of this general type is described, for example, by Milan Bier, U.S. Pat. No. 3,079,318. Such apparatus utilizes forced flow electrophoresis, in which the colloid permeable membrane serves as a filter through which liquid is forced by adjustment of pressure and flow rates through the cells. Such separations have been described by Smolka and Logan, Preparative Biochemistry, 2 (4), 329-45 (1972).